U.S. patent application number 10/798304 was filed with the patent office on 2004-09-16 for clamping mechanism of molding machine.
This patent application is currently assigned to Fanuc Ltd.. Invention is credited to Naito, Yasuo, Nishimura, Koichi.
Application Number | 20040180109 10/798304 |
Document ID | / |
Family ID | 32767939 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040180109 |
Kind Code |
A1 |
Nishimura, Koichi ; et
al. |
September 16, 2004 |
Clamping mechanism of molding machine
Abstract
A clamping mechanism of a molding machine, including a bed; a
stationary platen mounted on the bed, and carrying a stationary
mold; a guide bar arranged fixedly relative to the stationary
platen, and defining a longitudinal guiding axis; a first movable
platen arranged movably relative to the stationary platen along the
guiding axis, and carrying a movable mold; a support structure
interposed between the guide bar and the first movable platen, and
movably supporting the first movable platen on the guide bar along
the guiding axis; a second movable platen separate from the first
movable platen, and arranged movably relative to the stationary
platen along the guiding axis; a connecting member connecting the
first movable platen and the second movable platen to each other;
and a drive section for applying a drive force to the second
movable platen, to move the first movable platen and the second
movable platen along the guiding axis. The support structure
includes a spline engaging surface provided on the guide bar and a
ball spline nut provided in the first movable platen, the ball
spline nut being operatively engagable with the spline engaging
surface.
Inventors: |
Nishimura, Koichi;
(Susono-shi, JP) ; Naito, Yasuo; (Yamanashi,
JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Fanuc Ltd.
Yamanashi
JP
|
Family ID: |
32767939 |
Appl. No.: |
10/798304 |
Filed: |
March 12, 2004 |
Current U.S.
Class: |
425/592 ;
425/593; 425/595 |
Current CPC
Class: |
B29C 45/1761
20130101 |
Class at
Publication: |
425/592 ;
425/595; 425/593 |
International
Class: |
B29C 045/66 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2003 |
JP |
2003-066690 |
Claims
1. A clamping mechanism of a molding machine, comprising: a bed; a
stationary platen mounted on said bed, and carrying a stationary
mold; a guide bar arranged fixedly relative to said stationary
platen, and defining a longitudinal guiding axis; a first movable
platen arranged movably relative to said stationary platen along
said guiding axis, and carrying a movable mold; a support structure
interposed between said guide bar and said first movable platen,
and movably supporting said first movable platen on said guide bar
along said guiding axis; a second movable platen separate from said
first movable platen, and arranged movably relative to said
stationary platen along said guiding axis; a connecting member
connecting said first movable platen and said second movable platen
to each other; and a drive section for applying a drive force to
said second movable platen, to move said first movable platen and
said second movable platen along said guiding axis.
2. A clamping mechanism, as set forth in claim 1, wherein said
support structure comprises a spline engaging surface provided on
said guide bar and a ball spline nut provided in said first movable
platen; said ball spline nut being operatively engagable with said
spline engaging surface.
3. A clamping mechanism, as set forth in claim 2, wherein said
second movable platen includes a through-hole receiving said guide
bar without engaging with said spline engaging surface.
4. A clamping mechanism, as set forth in claim 2, further
comprising an end frame mounted on said bed at a location opposite
to said stationary platen about said first and second movable
platens; wherein said guide bar comprises a tie bar tying said
stationary platen to said end frame.
5. A clamping mechanism, as set forth in claim 2, further
comprising an end frame mounted on said bed at a location opposite
to said stationary platen about said first and second movable
platens and a tie bar, separate from said guide bar, defining a
second longitudinal guiding axis generally parallel to said guiding
axis of said guide bar; said tie bar tying said stationary platen
to said end frame.
6. A clamping mechanism, as set forth in claim 5, wherein said
first movable platen includes a first through-hole independent of
said ball spline nut and extending along said second guiding axis;
wherein said second movable platen includes a second through-hole
aligned along said second guiding axis with said first
through-hole; and wherein said tie bar is received in said first
and second through-holes.
7. A clamping mechanism, as set forth in claim 1, wherein said
connecting member connects said first and second movable platens in
a manner shiftable along said guiding axis relative to each
other.
8. A clamping mechanism, as set forth in claim 7, further
comprising a biasing member interposed between said first and
second movable platens, said biasing member elastically biasing
said first and second movable platens away from each other along
said guiding axis.
9. A clamping mechanism, as set forth in claim 7, further
comprising a biasing member interposed between said first and
second movable platens, said biasing member elastically biasing
said first and second movable platens toward each other along said
guiding axis.
10. A clamping mechanism, as set forth in claim 1, wherein said
first movable platen is made from a material having a rigidity
higher than that of said second movable platen.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a clamping mechanism of a
molding machine.
[0003] 2. Description of the Related Art
[0004] A conventional clamping mechanism of a molding machine
(e.g., an injection molding machine) generally includes a
stationary platen and an end frame (also referred to as a rear
platen), both mounted upright on a bed of the molding machine, a
plurality (normally, four) of tie bars bridging between the
stationary platen and the end frame, a movable platen having
through-holes individually receiving the tie bars and arranged
movably along the tie bars between the stationary platen and the
end frame, and a drive unit (e.g., a toggle unit) for driving the
movable platen. A movable mold is attached to the movable platen,
and a stationary mold is attached to the stationary platen. The
drive unit including a drive source, such as an electric motor or a
hydraulic cylinder, moves the movable platen, guided by the tie
bars, whereby the molds are clamped. In general, a pair of sliding
bearing bushes is disposed in each through-hole formed in the
movable platen, and each tie bar slidably penetrates through the
bushes.
[0005] In the conventional clamping mechanism as described above,
the sliding bearing structure, used in a mutually sliding portion
between the movable platen and each tie bar, inevitably creates a
clearance between the inner circumferential surface of the bearing
bush and the outer circumferential surface of the tie bar, which
results in a play in the sliding bearing. Therefore, the movable
platen is liable to tilt on the tie bars during a moving operation.
As a result, there is a tendency that a predetermined degree of
parallelism between the movable mold attached to the movable platen
and the stationary mold attached to the stationary platen is
deteriorated due to the moving operation of the movable paten. For
example, in a mold opening process, if the parallelism between the
molds is deteriorated at the instant when a mold release is caused
by the separation of the movable mold from the stationary mold, the
mold release timing of a molded article becomes irregular at
certain points in the molding surface of the stationary or movable
mold. In a case where a high-precision molded article, such as a
lens, is to be molded, an irregularity in the mold release timing
may result in a strain in the molded article, due to tensile
stress, etc., and thus may produce a defective molded article.
[0006] In order to solve the above problem, a solution has been
known, wherein a linear guide (an LM guide (trade name)) is
arranged on the bed of the molding machine for guiding the travel
of the movable platen, so that the movable platen is prevented from
tilting and the parallelism between the movable platen and the
stationary platen is maintained. In the solution using the linear
guide, the movable platen is supported at the bottom end thereof by
the linear guide, so that the tilting in the lower portion of the
movable platen is suppressed, but it is difficult to suppress the
tilting in the upper portion of the movable platen. Further, the
linear guide can prevent the movable platen from turning about an
axis in a moving direction of the movable platen (or an axial
direction of the tie bar), but it is difficult for the linear guide
to prevent the movable platen from turning about another axis
perpendicular to the above axis and parallel with the mold
attaching surface of the platen.
[0007] On the other hand, in a mold clamping process, the
stationary platen and/or the movable platen may be deformed or
strained due to a mutual pressing force applied to the stationary
and movable molds. If the stationary platen and/or the movable
platen is subjected to a strain, the mold-attaching surface of the
platen may be deformed, which may also result in a deterioration of
the parallelism between the stationary and movable molds and, thus,
in a deterioration of a molding accuracy.
[0008] As a solution to prevent such a strain or deformation in the
platen, for example, Japanese Utility Model Publication No. 2587035
(JP2587035Y2) discloses a clamping mechanism of an injection
molding machine, wherein at least one of a stationary platen and a
movable platen is provided, at an intermediate location as seen in
a platen-thickness direction in the regions of tie-bar insertion
holes formed at four corners of the platen, with a notch extending
from the outer circumference of the platen to the tie-bar insertion
holes. According to this arrangement, a pressing load applied to
the molds is absorbed by a deformation in the notched region of the
platen, and thus a deformation in the mold-attaching surface of the
platen is prevented.
[0009] Also, Japanese Unexamined Patent Publication (Kokai) No.
8-258103 (JP8-258103A) discloses a clamping mechanism of an
injection molding machine, wherein a support structure of the
stationary platen is formed into a tapered shape, such as a
rectangular pyramid or a truncated cone. According to this
arrangement, a pressing load generated during a mold clamping is
prevented from acting as a bending moment on the support structure,
due to the tapered shape of the latter, so that a deflection or
deformation in the support structure and the stationary platen is
prevented.
[0010] Further, Japanese Unexamined Patent Publication (Kokai) No.
11-170322 (JP11-170322A) discloses a clamping mechanism of an
injection molding machine, wherein a strain-preventing portion
(such as a lateral edge channel) is provided, on the movable
platen, between the pivot of the arm of a toggle mechanism and the
mold-attaching surface. According to this arrangement, a pressing
load generated during a mold clamping is absorbed by a deformation
in the strain-preventing portion of the movable platen, and thus a
deformation in the mold-attaching surface is prevented.
[0011] In the above conventional arts, a structure absorbing a
pressing load generated during a mold clamping process is provided
in the platen or the support structure thereof to prevent the
platen from being strained during, especially, the mold clamping.
In contrast, Japanese Patent Publication No. 3330578 (JP3330578B2)
discloses a clamping mechanism of a molding machine, such as an
injection molding machine, wherein a ball spline structure is
adopted, in place of a sliding-bearing structure, to a guiding
portion for the movable platen on the tie bar. According to this
arrangement, a guide having the ball spline structure makes it
possible for the movable platen to be always accurately translated
(or perform a parallel displacement) relative to the stationary
platen, so that a parallelism between the stationary mold and the
movable mold during a mold opening process can be stably
maintained. In this arrangement, it is required that the life of
the ball spline structure is long even under the influence of a
platen stress due to the pressing load during the mold
clamping.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
clamping mechanism, of a molding machine, which can stably
maintain, over a long period, the parallelism between a stationary
platen and a movable platen in a mold clamping process as well as
in a mold opening process.
[0013] To accomplish the above object, the present invention
provides a clamping mechanism, of a molding machine, comprising a
bed; a stationary platen mounted on the bed, and carrying a
stationary mold; a guide bar arranged fixedly relative to the
stationary platen, and defining a longitudinal guiding axis; a
first movable platen arranged movably relative to the stationary
platen along the guiding axis, and carrying a movable mold; a
support structure interposed between the guide bar and the first
movable platen, and movably supporting the first movable platen on
the guide bar along the guiding axis; a second movable platen
separate from the first movable platen, and arranged movably
relative to the stationary platen along the guiding axis; a
connecting member connecting the first movable platen and the
second movable platen to each other; and a drive section for
applying a drive force to the second movable platen, to move the
first movable platen and the second movable platen along the
guiding axis.
[0014] In the above clamping mechanism, it is advantageous that the
support structure comprises a spline engaging surface provided on
the guide bar and a ball spline nut provided in the first movable
platen, the ball spline nut being operatively engagable with the
spline engaging surface.
[0015] In this arrangement, the second movable platen may include a
through-hole receiving the guide bar without engaging with the
spline engaging surface.
[0016] The clamping mechanism may further comprise an end frame
mounted on the bed at a location opposite to the stationary platen
about the first and second movable platens, and the guide bar may
comprise a tie bar tying the stationary platen to the end
frame.
[0017] Alternatively, the clamping mechanism may further comprise
an end frame mounted on the bed at a location opposite to the
stationary platen about the first and second movable platens and a
tie bar, separate from the guide bar, defining a second
longitudinal guiding axis generally parallel to the guiding axis of
the guide bar, the tie bar tying the stationary platen to the end
frame.
[0018] In this arrangement, the first movable platen may include a
first through-hole independent of the ball spline nut and extending
along the second guiding axis, the second movable platen may
include a second through-hole aligned along the second guiding axis
with the first through-hole, and the tie bar may be received in the
first and second through-holes.
[0019] It is also advantageous that the connecting member connects
the first and second movable platens in a manner in which they are
shiftable, along the guiding axis, relative to each other.
[0020] In this arrangement, it is preferred that the clamping
mechanism further comprises a biasing member interposed between the
first and second movable platens, the biasing member elastically
biasing the first and second movable platens away from each other
along the guiding axis.
[0021] It is also preferred that the clamping mechanism further
comprises a biasing member interposed between the first and second
movable platens, the biasing member elastically biasing the first
and second movable platens toward each other along the guiding
axis.
[0022] It is also advantageous that the first movable platen is
made from a material having a rigidity higher than that of the
second movable platen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects, features and advantages of the
present invention will become more apparent from the following
description of preferred embodiments in connection with the
accompanying drawings, wherein:
[0024] FIG. 1 is a schematic front view showing a clamping
mechanism according to a first embodiment the present
invention;
[0025] FIG. 2 is a schematic front view showing the clamping
mechanism of FIG. 1 in a mold clamping state;
[0026] FIG. 3 is a schematic front view showing a clamping
mechanism according to a second embodiment the present
invention;
[0027] FIG. 4A is a schematic top plan view showing first and
second movable platens in the clamping mechanism of FIG. 3;
[0028] FIG. 4B is a side view showing the first and second movable
platens of FIG. 4A along an arrow IV;
[0029] FIGS. 5A and 5B are schematic views respectively showing a
connecting member in a clamping mechanism according to a third
embodiment the present invention;
[0030] FIG. 6 is a schematic front view showing the clamping
mechanism according to the third embodiment of the present
invention;
[0031] FIG. 7 is a schematic front view showing the clamping
mechanism of FIG. 6 in a mold opening state;
[0032] FIG. 8 is a schematic front view showing a clamping
mechanism according to a fourth embodiment of the present
invention;
[0033] FIG. 9 is a schematic front view showing the clamping
mechanism of FIG. 8 in a mold opening state;
[0034] FIG. 10 is a schematic front view showing a clamping
mechanism according to a fifth embodiment of the present
invention;
[0035] FIG. 11 is a schematic front view showing the clamping
mechanism of FIG. 10 in a mold opening state;
[0036] FIGS. 12A and 12B are schematic views respectively showing a
connecting member and a biasing member in a clamping mechanism
according to a sixth embodiment the present invention;
[0037] FIG. 13 is a schematic front view showing the clamping
mechanism according to the sixth embodiment of the present
invention;
[0038] FIG. 14 is a schematic front view showing the clamping
mechanism of FIG. 13 in a mold opening state;
[0039] FIGS. 15A and 15B are schematic views respectively showing a
connecting member and a biasing member in a clamping mechanism
according to a seventh embodiment the present invention;
[0040] FIG. 16 is a schematic front view showing the clamping
mechanism according to the seventh embodiment of the present
invention;
[0041] FIG. 17 is a schematic front view showing the clamping
mechanism of FIG. 16 in a mold opening state;
[0042] FIG. 18 is a schematic front view showing a clamping
mechanism according to an eighth embodiment of the present
invention; and
[0043] FIG. 19 is a schematic front view showing the clamping
mechanism of FIG. 18 in a mold opening state.
DETAILED DESCRIPTION
[0044] The embodiments of the present invention are described below
in detail, with reference to the accompanying drawings. In the
drawings, the same or similar components are denoted by common
reference numerals.
[0045] The basic concepts of a clamping mechanism of a molding
machine according to the present invention are directed to a first
mode wherein an auxiliary movable platen (referred to as a first
movable platen in this application) is arranged between a movable
platen linked to a drive section (referred to as a second movable
platen in this application) and a movable mold, and a ball spline
structure is provided as a guide/support structure for the first
movable platen, as well as a second mode wherein the first and
second movable platens are engaged with each other while ensuring a
play or a mutual displacement, by using a connecting member.
According to the above basic concepts, it is effected that the
parallelism between the fixed platen and the first movable platen,
respectively carrying molds, is maintained, and that a reduction in
the life of the ball spline structure, due to an uneven load
distribution axially along a ball spline nut, is prevented.
[0046] Referring to the drawings, FIGS. 1 and 2 show a clamping
mechanism 10 of a molding machine, according to a first embodiment
realizing the above-described first concept of the present
invention. The clamping mechanism 10 includes a bed 12; a
stationary platen 14 mounted on the bed 12, and carrying a
stationary mold 16; a guide bar 18 arranged fixedly relative to the
stationary platen 14, and defining a longitudinal guiding axis 18a;
a first movable platen 20 arranged movably relative to the
stationary platen 14 along the guiding axis 18a, and carrying a
movable mold 22; a support structure 24 interposed between the
guide bar 18 and the first movable platen 20, and movably
supporting the first movable platen 20 on the guide bar 18 along
the guiding axis 18a; a second movable platen 26 separate from the
first movable platen 20, and arranged movably relative to the
stationary platen 14 along the guiding axis 18a; a connecting
member 28 connecting the first movable platen 20 and the second
movable platen 26 to each other; and a drive section 30 for
applying a drive force to the second movable platen 26, to move the
first movable platen 20 and the second movable platen 26 along the
guiding axis 18a. The clamping mechanism 10 further includes an end
frame 32 mounted on the bed 12 at a location opposite to the
stationary platen 14 about the first and second movable platens 20,
26.
[0047] The guide bar 18 is structured as a tie bar 18 tying the
stationary platen 14 and the end frame 32 to each other. In the
illustrated embodiment, the mutually opposing surfaces of the
stationary platen 14 and of the end frame 32, both uprightly
provided on the bed 12, are of rectangular profiles, and four tie
bars 18 are arranged respectively at the four corners of the
opposing surfaces (FIG. 1 illustrates only two tie bars 18).
[0048] Each tie bar 18 is secured at one end to the stationary
platen 14 by a fastening element such as a nut, and is attached at
the other end to the end frame 32 through a mold-thickness
adjusting nut 34 in a relatively shiftable manner. Pinions 36 are
secured respectively to the mold-thickness adjusting nuts 34, and a
chain (not shown) is wrapped around the pinions 36 provided
respectively to the four tie bars 18. When the chain is driven by a
not-shown drive source for a mold-thickness adjustment so as to
synchronously rotate the nuts 34 of the tie bars 18, the end frame
32 is shifted on the bed 12 along the tie bars 18. Thereby, the
distance between the end frame 32 and the stationary platen 14 is
adjusted, and it is thus possible to adjust a clamping force
depending on the thickness of the molds as used.
[0049] Each tie bar (a guide bar) 18 is received, in a relatively
movable manner, in through-holes formed in both the first movable
platen 20 and the second movable platen 26 in such a manner as to
be aligned with each other along the guiding axis 18a. Each tie bar
18 is provided with a spline engaging surface 38 formed by plural
ribs or grooves extending along the guiding axis 18a, at least over
a predetermined surface area over which the first movable platen 20
slides along the tie bar 18. In other words, the tie bar 18
functions as a spline shaft over the area provided with the spline
engaging surface 38. On the other hand, each through-hole in the
first movable platen 20 for receiving the tie bar 18 is provided
with a ball spline nut 40 operatively engagable with the spline
engaging surface 38 of the tie bar 18. The spline engaging surface
38 on the tie bar 18 and the corresponding ball spline nut 40 in
the first movable platen 20 cooperate with each other to constitute
the support structure 24. In the illustrated embodiment, a pair of
ball spline nuts 40 is provided in each through-hole of the first
movable platen 20.
[0050] In contrast, each through-hole in the second movable platen
26 for receiving the tie bar 18 is provided with a sliding bearing
bush 42 which is not engagable with the spline engaging surface 38
on the tie bar 18. Each sliding bearing bush 42 slidably receives
the corresponding tie bar 18 through a slight clearance
therebetween, whereby the second movable platen 26 is guided along
the guiding axis 18a. In the illustrated embodiment, a pair of
sliding bearing bushes 42 is provided in each through-hole of the
second movable platen 26. Also, instead of using the sliding
bearing bushes 42, the inner diameter of each through-hole of the
second movable platen 26 may be selected to be larger than the
outer diameter of the tie bar 18 so that the through-hole of the
second movable platen 26 can receive the tie bar 18 in a
non-contact manner.
[0051] The connecting member 28 is formed from a fastening element
such as a bolt, and locally fixes the first movable platen 20 to
the second movable platen 26 at the position of the connecting
member 28. In the illustrated embodiment, two connecting members 28
are provided at locations in proximity with the centers of the
respective movable platens 20, 26. The local fixation of the
connecting member 28 serves to permit the mutual abutting surfaces
of the movable platens 20, 26 to slightly slide relative to each
other when the movable platens 20, 26 are deflected.
[0052] The drive section 30 includes a toggle unit 44 arranged
between the end frame 32 and the second movable platen 26, and a
drive source 46, such as a servo motor, for driving a cross head
44a of the toggle unit 44. The toggle unit 44 and the drive source
46 are mounted on the end frame 32, and a pair of arms 44b of the
toggle unit 44 are joined at their distal ends to the top and
bottom areas of the second movable platen 26, respectively.
[0053] The stationary mold 16 and the movable mold 22 are attached
respectively to the mutually opposing mold-attaching surfaces 14a,
20a of the stationary platen 14 and the first movable platen 20.
When the drive source 46 is actuated to drive the toggle unit 44,
so as to move the second movable platen 26 and the first movable
platen 20 along the tie bars 18 in the direction of guiding axis
18a, the molds 16, 22 are operated to open or close (a mold opening
or clamping operation).
[0054] FIG. 2 illustrates a mold clamping state. Under a clamping
force applied from the driving section 30, the second movable
platen 26 and the stationary platen 14 are slightly deformed as
typically shown by broken lines. In this connection, the second
movable platen 26 is directly linked to the toggle unit 44, so that
the strain or deformation thereof becomes greater. In contrast, the
first movable platen 20 is not directly linked to the toggle unit
44 and the second movable platen 26 is interposed therebetween, so
that the strain or deformation of the first movable platen 20 is
relieved, with the aid of the slight sliding between the mutual
abutting surfaces of the movable platens 20, 26 as described.
Therefore, during the mold clamping state, the strain of the mold
attaching surface 20a of the first movable platen 20 is suppressed
and, thus, it is possible to prevent the parallelism between the
mold attaching surfaces 14a, 20a, of the stationary platen 14 and
the first movable platen 20, from being deteriorated.
[0055] Further, in a condition where the stationary mold 16 is not
in contact with the movable mold 22 during the mold opening state,
the second movable platen 26 linked to the toggle unit 44 is liable
to be deformed or strained under the influence of the production
error of the toggle mechanism and/or the weight thereof. According
to the clamping mechanism 10, it is also possible, during the mold
opening state, to prevent the strain in the second movable platen
26 from being transferred to the first movable platen 20, and thus
to maintain the parallelism between the mold attaching surfaces
14a, 20a of the stationary platen 14 and the first movable platen
20 as well as the parallelism between the stationary mold 16 and
the movable mold 22.
[0056] Also, in the clamping mechanism 10, the support structure 24
between the first movable platen 20 and the tie bars (or guide
bars) 18 is constituted by a ball spline structure as already
described. In the usual ball spline structure, there is almost no
clearance between a spline shaft and a ball spline nut, because a
plurality of balls are engaged with the spline engaging surface
(e.g., a ball rolling groove) of the spline shaft under a certain
pressure. The support structure 24 adopting such a ball spline
structure serves to substantially eliminate a play between the tie
bar 18 and the first movable platen 20.
[0057] Moreover, in the illustrated embodiment, the tie bars 18 are
received, over the spline shaft length (or the spline engaging
surface 38) thereof, in the ball spline nuts 40 provided at four
corners of the first movable platen 20, so that it is possible to
effectively prevent the first movable platen 20 from being tilted.
In other words, the first movable platen 20 is bound on the four
tie bars 18 through the ball spline structure, which makes it
possible for the first movable platen 20 to be always accurately
translated (or perform a parallel displacement) relative to the
stationary platen 14, without causing a rotation of the first
movable platen about the guiding axis 18a as well as respective
rotations thereof about vertical and horizontal axes perpendicular
to the guiding axis 18a. It should be noted that such a rotation
inhibiting effect can be obtained by not only the above
configuration using four tie bars 18 but also the other
configuration using at least two tie bars 18 located along a
diagonal line.
[0058] Accordingly, the mold attaching surfaces 14a, 20a of the
stationary platen 14 and the first movable platen 20 are maintained
in parallel at all times including the mold clamping and opening
states, and also the molding surfaces of the stationary and movable
molds 16, 22 attached respectively to the mold attaching surfaces
14a, 20a are maintained in a proper positional correlation.
Particularly, in a mold release step, it is possible to effectively
prevent the mold release timing of a molded article from becoming
irregular at certain points in the molding surfaces. As a result,
it is possible to surely prevent the molded article from being
subjected to a strain due to an irregular or non-uniform
mold-release timing, and thus to extremely favorably produce a
high-precision article such as a lens.
[0059] Besides, in addition to the provision of the above-described
ball spline structure for the support structure 24, the strain in
the first movable platen 20 carrying the movable mold 22 is
relieved because the first movable platen 20 is indirectly linked
to the toggle unit 44, as already described, so that it is possible
to eliminate the disadvantage that the ball spline nut 40 provided
in the first movable platen 20 comes into contact with the spline
engaging surface 38 of the corresponding tie bar 18 under a
non-uniformly distributed load along the guiding axis 18a. As a
result, it is possible to significantly increase the life of the
spline engaging surface 38 of the tie bar 18 as well as of the ball
spline nut 40.
[0060] In the above-described configuration, the first and second
movable platens 20, 26 connected to each other can be made from
materials different from each other. In particular, it is
advantageous that the first movable platen 20 is made from a
material having a rigidity higher than the rigidity of material of
the second movable platen 26. In this connection, a material having
high rigidity means that the material has a large modulus of
longitudinal elasticity. For example, in the case where the second
movable platen 26 is made from a gray cast iron or a spheroidal
graphite cast iron, the first movable platen 20 can be made from a
material having about twice modulus of longitudinal elasticity of
the former materials, such as a rolled steel for general
structures, a carbon steel for general structures or an alloy steel
for general structures.
[0061] The second movable platen 26 has a relatively complex
structure due to, e.g., the provision of the toggle unit 44 linked
thereto. In general, a material having high rigidity (or a large
modulus of longitudinal elasticity) is difficult to process, which
may result in the increase in a production cost, so that it is
advantageous to make the second movable platen 26 from a material
having a lower rigidity facilitating a casting process. On the
other hand, the first movable platen 20 has a relatively simple
structure and does not require complex machining. Therefore, the
first movable platen 20 can be made from a material having high
rigidity, without increasing the production cost. As a result, it
is possible to further effectively relieve the strain in the first
movable platen 20, which makes it possible to stably maintain the
parallelism between the stationary and movable molds 16, 22, and
thus to increase the life of the ball spline structure.
[0062] It should be noted that, in the above embodiment, the number
of the ball spline nuts 40 provided in each tie-bar receiving
through-hole of the first movable platen 20 is not limited to two
as illustrated, but may be one or three or more. As a ball-spline
engaging length is increased by, e.g., increasing the number of the
ball spline nuts 40, the effect of inhibiting the tilt or rotation
of the first movable platen 20 is improved, which further
stabilizes the translation or parallel displacement of the first
movable platen 20.
[0063] Further, the first and the second movable platens 20, 26 may
be mounted on the base 12 through known platen supports 48 (FIG.
1), so as to positively adjust the tilting of the movable platens
20, 26 by using the platen supports 48. The platen support 48 may
have a construction as disclosed in, for example, U.S. Pat. No.
3,674,400 issued Jul. 4, 1972 to Sauerbruch et al., the teachings
of which are hereby incorporated by reference.
[0064] FIG. 3 shows a clamping mechanism 50 according to a second
embodiment realizing the first concept of the present invention.
The clamping mechanism 50 of the second embodiment has a
configuration substantially identical to the clamping mechanism 10
of the first embodiment, except for the provisions of a tie bar and
a guide bar, separate from each other, and of a ball spline
structure only for the guide bar. Therefore, corresponding
components are denoted by common reference numerals and the
detailed descriptions thereof are not repeated.
[0065] The clamping mechanism 50 includes a guide bar 18 arranged
fixedly relative to a stationary platen 14; a support structure 24
having a ball spline structure and movably supporting a first
movable platen 20 on the guide bar 18 along the guiding axis 18a
thereof; and a tie bar 52, separate from the guide bar 18, defining
a second longitudinal guiding axis 52a generally parallel to the
guiding axis 18a, the tie bar 52 tying the stationary platen 14 and
an end frame 32 to each other.
[0066] In the illustrated embodiment, the mutually opposing
surfaces of the stationary platen 14 and of the end frame 32 have
rectangular profiles, and four tie bars 52 are arranged
respectively at the four corners of the opposing surfaces. In the
same way as the tie bar 18 of the first embodiment, each tie bar 52
is secured at one end to the stationary platen 14, and is attached
at the other end to the end frame 32 through a mold-thickness
adjusting nut 34 in a relatively shiftable manner. Two guide bars
18 are arranged respectively at locations laterally outside a pair
of tie bars 52 disposed along a diagonal line. Each guide bar 18 is
secured at one end to the lateral extension 14b of the stationary
platen 14, and is slidably supported at the other end on the
lateral extension 32a of the end frame 32.
[0067] Each guide bar 18 is received, in a relatively movable
manner, in a through-hole formed in the lateral extension 20b of
the first movable platen 20. Each guide bar 18 is provided with a
spline engaging surface 38 formed by plural ribs or grooves
extending along the guiding axis 18a, at least over a predetermined
surface area over which the first movable platen 20 slides along
the guide bar 18. In other words, the guide bar 18 functions as a
spline shaft over the area provided with the spline engaging
surface 38. On the other hand, as shown in FIGS. 4A and 4B, each
through-hole in the first movable platen 20 for receiving the guide
bar 18 is provided with a ball spline nut 40 operatively engagable
with the spline engaging surface 38 of the guide bar 18. The spline
engaging surface 38 on the guide bar 18 and the corresponding ball
spline nut 40 in the first movable platen 20 cooperate with each
other to constitute the support structure 24. In the illustrated
embodiment, a pair of ball spline nuts 40 is provided in each
through-hole of the first movable platen 20.
[0068] Each tie bar 52 is received, in a relatively movable manner,
in through-holes formed in both the first movable platen 20 and the
second movable platen 26 in such a manner as to be aligned with
each other along the guiding axis 52a. Each tie bar 52 is a rod
member having a substantially smooth outer-circumferential surface.
As shown in FIGS. 4A and 4B, each through-hole in the second
movable platen 26 for receiving the tie bar 52 is provided with a
sliding bearing bush 42, in the same way as the first embodiment.
Each sliding bearing bush 42 slidably receives the corresponding
tie bar 52 through a slight clearance therebetween, whereby the
second movable platen 26 is guided along the guiding axis 52a. On
the other hand, the first movable platen 20 receives the tie bars
52 in respective through-holes 54 in a non-contact manner, the
inner diameter of each through-hole 54 being larger than the outer
diameter of tie bar 52.
[0069] Thus, in the clamping mechanism 50, the first movable platen
20 is supported on the guide bars 18 through the support structure
24 having the ball spline structure, while the second movable
platen 26 is engaged with the tie bars 52 through the sliding
bearing bushes 42, and both movable platens 20, 26 are moved along
the guiding axis 18a (52a) by the driving operation of a drive
section 30. It will be appreciated that the clamping mechanism 50
having the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanism 10 of
the first embodiment. Further, in the clamping mechanism 50, the
guide bars 18 are provided separately from the tie bars 52, so that
the function of the guide bars 18 and the support structure 24
having the ball spline structure, for maintaining the parallelism
of the first movable platen 20, is effected separately from the tie
bars 52. As a result, it is possible to prevent the strain or
deformation in the tie bars 52, resulted from, e.g., a stress due
to the drive section 30, from being transferred to the first
movable platen 20, and thus improve the effect of inhibiting the
tilt or rotation of the first movable platen 20, which further
stabilizes the translation or parallel displacement of the first
movable platen 20. Moreover, it is possible to further increase the
life of the ball spline structure.
[0070] Although, in the illustrated embodiment, two guide bars 18
arranged along a diagonal line are used, the present invention is
not limited thereto, but additional guide bars 18 arranged along
another diagonal line may be used. In this arrangement, the ball
spline nuts 40 are also provided at the other two corners of the
first movable platen 20, as shown by broken lines in FIG. 4B.
Further, the guide bar 18 is not restricted to the illustrated
configuration bridging between the stationary platen 14 and the end
frame 32, but may be provided separately from both the stationary
platen 14 and the end frame 32.
[0071] Although, the respective embodiments as described above are
directed to the configuration wherein the toggle unit 44 is used in
the drive section 30, the characteristic arrangements of the
present invention may also be applied to a clamping mechanism
including a direct-pressurizing drive section wherein the first and
second movable platen 20, 26 are directly driven by the drive
source 46 such as a hydraulic cylinder or a servo motor, without
using the toggle unit 44. It will be appreciated that, in this
configuration, characteristic effects equivalent to those of the
respective embodiments can also be obtained.
[0072] FIGS. 5A to 7 show a clamping mechanism 60 according to a
third embodiment realizing the second concept of the present
invention. The clamping mechanism 60 of the third embodiment has a
configuration substantially identical to the clamping mechanism 10
of the first embodiment, except that the support structure
supporting the first movable platen is formed from a sliding
bearing structure, and that the first and second movable platens
are mutually shiftably connected to each other by the connecting
member. Therefore, corresponding components are denoted by common
reference numerals and the detailed descriptions thereof are not
repeated.
[0073] The clamping mechanism 60 includes a stationary platen 14
mounted on a bed 12; a first movable platen 20 arranged movably
relative to the stationary platen 14 along the guiding axis 18a of
a guide bar 18; a support structure 24 having a sliding bearing
structure and movably supporting the first movable platen 20 on the
guide bar 18 along the guiding axis 18a; a second movable platen 26
separate from the first movable platen 20, and arranged movably
relative to the stationary platen 14 along the guiding axis 18a;
and a connecting member 28 connecting the first movable platen 20
and the second movable platen 26 to each other in a manner
shiftable along the guiding axis 18a relative to each other (FIG.
6).
[0074] As shown in FIG. 6, the guide bar 18, in the clamping
mechanism 60, is structured as a tie bar 18 tying the stationary
platen 14 and the end frame 32 to each other. In the illustrated
embodiment, the mutually opposing surfaces of the stationary platen
14 and of the end frame 32 are of rectangular profiles, and four
tie bars 18 are arranged respectively at the four corners of the
opposing surfaces. Each tie bar 18 is received, in a relatively
movable manner, in through-holes formed in both the first movable
platen 20 and the second movable platen 26 in such a manner as to
be aligned with each other along the guiding axis 18a. Each tie bar
18 is a rod member having a substantially smooth
outer-circumferential surface. Each through-hole in the first and
second movable platens 20, 26 for receiving the tie bar 18 is
provided with a sliding bearing bush 42. Each sliding bearing bush
42 slidably receives the corresponding tie bar 18 through a slight
clearance therebetween, whereby the first and second movable
platens 20, 26 are guided along the guiding axis 18a. Thus, in the
clamping mechanism 60, the first and second movable platens 20, 26
are engaged with the tie bars 18 through the support structure 24
having the sliding bearing structure, and are moved along the
guiding axis 18a by the driving operation of a drive section
30.
[0075] As shown in FIGS. 5A and 5B, the connecting member 28 is
formed from a fastening element having a bulging head 28a and a
stem 28b, such as a bolt, and locally connects the first movable
platen 20 to the second movable platen 26 in a mutually shiftable
manner at the position of the connecting member 28. In the
illustrated embodiment, two connecting members 28 are provided at
locations in proximity with the centers of the respective movable
platens 20, 26 (FIG. 6).
[0076] Each connecting member 28 is secured at one end length of
the stem 28b to the second movable platen 26, and is attached at
the other end length, including the head 28a, to the first movable
platen 20 in a manner displaceable along the guiding axis 18a (FIG.
6). To ensure this relative displacement (i.e., "a play"), the
first movable platen 20 is provided with stepped through-holes 62,
each receiving the head 28a and the stem 28b of the connecting
member 28 in an axially movable manner and formed in parallel with
the guiding axis 18a of the tie bar 18. Each stepped through-hole
62 includes a larger-diameter hole portion 62a for receiving the
head 28a of the connecting member 28, and a smaller-diameter hole
portion 62b for receiving the stem 28b of the connecting member 28.
The larger-diameter hole portion 62a of the stepped through-hole 62
has an axial length depending on the required distance of the
relative displacement of the first and second movable platens 20,
26. It is preferred that the larger-diameter hole portion 62a has a
diameter permitting the head 28a of the connecting member 28 to be
received therein with a sufficient gap defined therebetween. Also,
it is preferred that the smaller-diameter hole portion 62d has a
diameter permitting the stem 28b of the connecting member 28 to be
received therein with a slight gap defined therebetween. Of course,
the smaller-diameter hole portion 62d may receive the stem 28b in a
slidable manner.
[0077] FIG. 5A illustrates a state where the second movable platen
26 is in close contact with the first movable platen 20
(corresponding to the mold clamping state shown in FIG. 6), and
FIG. 5B illustrates a state where the second movable platen 26 is
parted from the first movable platen 20 (corresponding to the mold
opening state shown in FIG. 7). In the state of FIG. 5B, the head
28a of the connecting member 28 is abutted to a shoulder face 62c
located at a boundary between the larger-diameter hole portion 62a
and the smaller-diameter hole portion 62b of the stepped
through-hole 62 in the first movable platen 20, so that the second
movable platen 26 and the first movable platen 20 cannot be spaced
by more than a predetermined mutual shifting distance.
[0078] Referring to FIG. 7, when the toggle unit 44 is driven to
move the second movable platen 26 and the first movable platen 20
in a mold-opening direction (shown by an arrow a), the second
movable platen 26 first starts moving toward the end frame 32. In
this connection, the first movable platen 20 is connected to the
second movable platen 26 through the "play" obtained by the
connecting members 28, and thereby remains stationary until the
second movable platen 26 has been moved by the distance
corresponding to the "play". When the second movable platen 26
moves by the distance exceeding the "play", the first movable
platen 20 then starts moving toward the end frame 32 while being
pulled by the connecting members 28, and thus the molds 16, 22 are
opened.
[0079] Therefore, in the case where the second movable platen 26,
linked to the toggle unit 44, is strained or deformed due to, e.g.,
the weight of the toggle unit 44 during the mold opening state
where the stationary mold 16 is not in contact with the movable
mold 22, as shown by a broken line in FIG. 7, the "play" between
the respective connecting members 28 and the stepped through-holes
62 acts to absorb such a strain in the second movable platen 26. As
a result, the first movable platen 20 is able to move in
translation or parallel displacement, without being affected by the
strain in the second movable platen 26, so that the parallelism
between the mold attaching surfaces 14a, 20a of the stationary
platen 14 and the first movable platen 20, as well as the
parallelism between the stationary mold 16 and the movable mold 22
are maintained.
[0080] The correlation between the first and second movable platens
20, 26 and the connecting members 28 may be reversed from that in
the illustrated embodiment. In other words, each connecting member
may be constructed as to be secured at one end length of the stem
28b to the first movable platen 20, and is mutually displaceably
received at the other end length, including the head 28a, in a
stepped through-hole (not shown) formed in the second movable
platen 26 so as to be attached to the second movable platen 26 in a
manner displaceable along the guiding axis 18a.
[0081] FIGS. 8 and 9 show a clamping mechanism 70 according to a
fourth embodiment realizing the second concept of the present
invention, in mold clamping and opening states, respectively. The
clamping mechanism 70 of the fourth embodiment has a configuration
substantially identical to the clamping mechanism 60 of the third
embodiment, except that the support structure supporting the first
movable platen is formed from a ball spline structure. Therefore,
corresponding components are denoted by common reference numerals
and the detailed descriptions thereof are not repeated.
[0082] The clamping mechanism 70 includes a stationary platen 14
mounted on a bed 12; a first movable platen 20 arranged movably
relative to the stationary platen 14 along the guiding axis 18a of
a guide bar 18; a support structure 24 having a ball spline
structure and movably supporting the first movable platen 20 on the
guide bar 18 along the guiding axis 18a; a second movable platen 26
separate from the first movable platen 20, and arranged movably
relative to the stationary platen 14 along the guiding axis 18a;
and a connecting member 28 connecting the first movable platen 20
and the second movable platen 26 to each other in a manner
shiftable along the guiding axis 18a relative to each other.
[0083] The support structure 24 having the ball spline structure in
the clamping mechanism 70 is substantially the same as the support
structure 24 in the first embodiment (FIG. 1). Thus, the guide bar
18 is structured as a tie bar 18 tying the stationary platen 14 and
the end frame 32 to each other, and each of four tie bars 18 is
provided with a spline engaging surface 38 at least over a
predetermined surface area over which the first movable platen 20
slides along the tie bar 18. On the other hand, each through-hole
in the first movable platen 20 for receiving the tie bar 18 is
provided with a ball spline nut 40 operatively engagable with the
spline engaging surface 38 of the tie bar 18. In contrast, each
through-hole in the second movable platen 26 for receiving the tie
bar 18 is provided with a sliding bearing bush 42 which is not
engagable with the spline engaging surface 38 on the tie bar
18.
[0084] The connecting member 28 is the same as the connecting
member 28 in the third embodiment, and two connecting members 28
are provided at locations in proximity with the centers of the
respective movable platens 20, 26. Each connecting member 28 is
secured at one end length of a stem 28b (FIG. 5A) to the second
movable platen 26, and is received at the other end length,
including a head 28a (FIG. 5A), in a stepped through-hole 62 of the
first movable platen 20 so as to be attached to the first movable
platen 20 in a manner displaceable along the guiding axis 18a (FIG.
8).
[0085] Referring to FIG. 9, when the toggle unit 44 is driven to
move the second movable platen 26 and the first movable platen 20
in a mold-opening direction (shown by an arrow ax), the second
movable platen 26 first starts moving toward the end frame 32 along
the tie bars 18 under the support of the sliding bearing structure.
In this connection, the first movable platen 20 is connected to the
second movable platen 26 through the "play" obtained by the
connecting members 28, and thereby remains stationary until the
second movable platen 26 has been moved by the distance
corresponding to the "play". When the second movable platen 26
moves by the distance exceeding the "play", the first movable
platen 20 then starts moving toward the end frame 32 along the tie
bars 18 under the support of the support structure 24 having the
ball spline structure, while being pulled by the connecting members
28, and thus the molds 16, 22 are opened.
[0086] It will be appreciated that the clamping mechanism 70 having
the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanism 60 of
the third embodiment. Further, in the clamping mechanism 70, the
ball spline structure is adopted to the support structure 24 for
the first movable platen 20, so that it is possible to maintain the
parallelism between the mold attaching surfaces 14a, 20a of the
stationary platen 14 and the first movable platen 20, as well as
the parallelism between the stationary mold 16 and the movable mold
22. Moreover, the connecting member 28 serves to permit the first
movable platen 20 to move in translation free of the strain in the
second movable platen 26, so that it is possible to significantly
increase the life of the ball spline structure.
[0087] FIGS. 10 and 11 show a clamping mechanism 80 according to a
fifth embodiment realizing the second concept of the present
invention, in mold clamping and opening states, respectively. The
clamping mechanism 80 of the fifth embodiment has a configuration
substantially identical to the clamping mechanism 70 of the fourth
embodiment, except for the provision of a tie bar separate from the
guide bar. Therefore, corresponding components are denoted by
common reference numerals and the detailed descriptions thereof are
not repeated.
[0088] The clamping mechanism 80 includes a guide bar 18 arranged
fixedly relative to a stationary platen 14; a support structure 24
having a ball spline structure and movably supporting a first
movable platen 20 on the guide bar 18 along the guiding axis 18a
thereof; a tie bar 52, separate from the guide bar 18, defining a
second longitudinal guiding axis 52a generally parallel to the
guiding axis 18a and tying the stationary platen 14 and an end
frame 32 to each other; and a connecting member 28 connecting the
first movable platen 20 and the second movable platen 26 to each
other in a manner shiftable along the guiding axis 18a relative to
each other.
[0089] The support structure 24 having the ball spline structure in
the clamping mechanism 80 is substantially the same as the support
structure 24 in the second embodiment (FIG. 3). Thus, each of two
guide bars 18 disposed along a diagonal line is provided with a
spline engaging surface 38 at least over a predetermined surface
area over which the first movable platen 20 slides along the guide
bar 18. On the other hand, each through-hole in the first movable
platen 20 for receiving the guide bar 18 is provided with a ball
spline nut 40 operatively engagable with the spline engaging
surface 38 of the guide bar 18. Each of four tie bars 52 is a rod
member having a substantially smooth outer-circumferential surface,
and each through-hole in the second movable platen 26 for receiving
the tie bar 52 is provided with a sliding bearing bush 42.
[0090] The connecting member 28 is the same as the connecting
member 28 in the fourth embodiment, and two connecting members 28
are provided at locations in proximity with the centers of the
respective movable platens 20, 26. Each connecting member 28 is
secured at one end length of a stem 28b (FIG. 5A) to the second
movable platen 26, and is received at the other end length,
including a head 28a (FIG. 5A), in a stepped through-hole 62 of the
first movable platen 20 so as to be attached to the first movable
platen 20 in a manner displaceable along the guiding axis 18a (FIG.
10).
[0091] It will be appreciated that the clamping mechanism 80 having
the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanism 70 of
the fourth embodiment. Further, in the clamping mechanism 80, the
guide bar 18 is separate from the tie bar 52, so that it is
possible to prevent the strain or deformation in the tie bars 52
from being transferred to the first movable platen 20, and thus
improve the effect of inhibiting the tilt or rotation of the first
movable platen 20, which further stabilizes the translation or
parallel displacement of the first movable platen 20. Moreover, it
is possible to further increase the life of the ball spline
structure.
[0092] FIGS. 12A to 14 show a clamping mechanism 90 according to a
sixth embodiment realizing the second concept of the present
invention. The clamping mechanism 90 of the sixth embodiment has a
configuration substantially identical to the clamping mechanism 70
of the fourth embodiment, except for the provision of a biasing
member elastically biasing the first and second movable platens in
a direction away from each other. Therefore, corresponding
components are denoted by common reference numerals and the
detailed descriptions thereof are not repeated.
[0093] The clamping mechanism 90 includes a stationary platen 14
mounted on a bed 12; a first movable platen 20 arranged movably
relative to the stationary platen 14 along the guiding axis 18a of
a guide bar 18; a support structure 24 having a ball spline
structure and movably supporting the first movable platen 20 on the
guide bar 18 along the guiding axis 18a; a second movable platen 26
separate from the first movable platen 20, and arranged movably
relative to the stationary platen 14 along the guiding axis 18a; a
connecting member 28 connecting the first movable platen 20 and the
second movable platen 26 to each other in a manner shiftable along
the guiding axis 18a relative to each other; and a biasing member
92 interposed between the first movable platen 20 and the second
movable platen 26 and elastically biasing the first and second
movable platens 20, 26 away from each other along the guiding axis
18a (FIG. 13).
[0094] As shown in FIGS. 12A and 12B, the biasing member 92 is
formed from an elastic element such as a compression coil spring,
and elastically biases the first and second movable platen 20, 26
away from each other at the position of the connecting member 28.
In the illustrated embodiment, two biasing members 92 formed from
compression coil springs are respectively provided to the two
connecting members 28 provided at locations in proximity with the
centers of the movable platens 20, 26 (FIG. 13).
[0095] Each biasing member 92 is abutted at one end thereof to the
surface of the second movable platen 26 facing the first movable
platen 20, and is received at the other end length in a receptacle
hole portion 62d of a stepped through-hole 62 in the first movable
platen 20, which is recessed from the opening of the through-hole
62 facing the second movable platen 26 so as to enclose the stem
28b of the connecting member 28, so that the biasing member 92 is
arranged to surround the stem 28b of the connecting member 28.
Consequently, the biasing members 92 bias the first movable platen
20 relative to the second movable platen 26 in the direction toward
the stationary platen 14 (shown by an arrow i).
[0096] In a state where the second movable platen 26 is in close
contact with the first movable platen 20 as shown in FIG. 12A
(corresponding to the mold clamping state shown in FIG. 13), the
biasing member 92 is compressed in the receptacle hole portion 62d
of the stepped through-hole 62, so as to bias the first movable
platen 20 in the arrowed direction P. From this state, when the
first and second movable platens 20, 26 move toward the end frame
32, the first and second movable platens 20, 26 are shifted into a
mutually parted state by the function of the connecting member 28
as already described (FIG. 12B). In this state (corresponding to
the mold opening state shown in FIG. 14), the head 28a of the
connecting member 28 is abutted to a shoulder face 62c of the
stepped through-hole 62 so as to anchor the second movable platen
26 and the first movable platen 20 at a predetermined correlative
position, and therefore, the biasing member 92 is also compressed
in the receptacle hole portion 62d of the stepped through-hole 62
to bias the first movable platen 20 in the arrowed direction P.
[0097] Referring to FIG. 14, when the toggle unit 44 is driven to
move the second movable platen 26 and the first movable platen 20
in a mold-opening direction (shown by an arrow a), the second
movable platen 26 first starts moving toward the end frame 32 along
the tie bars 18 under the support of the sliding bearing structure.
In this connection, the first movable platen 20 is connected to the
second movable platen 26 through the "play" obtained by the
connecting members 28, and thereby remains stationary until the
second movable platen 26 has been moved by the distance
corresponding to the "play". When the second movable platen 26
moves by the distance exceeding the "play", the first movable
platen 20 then starts moving toward the end frame 32 along the tie
bars 18 under the support of the support structure 24 having the
ball spline structure, while being pulled by the connecting members
28, and thus the molds 16, 22 are opened.
[0098] In this regard, during a period from an instant when the
second movable platen 26 starts moving to an instant when the first
movable platen 20 starts moving, the biasing members 92 continue to
elastically bias the first movable paten 20 toward the stationary
platen 14. Also, during a period when the first movable platen 20
moves together with the second movable platen 26 through the
connecting members 28, the biasing members 92 continue to
elastically bias the first movable paten 20 toward the stationary
platen 14. Consequently, it is possible to effectively suppress an
unintentional unstable travel of the first movable platen 20, by
the elastic biasing force of the biasing members 92, which may
otherwise be caused due to the mutual parting action of the first
and second movable platens 20, 26.
[0099] It will be appreciated that the clamping mechanism 90 having
the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanism 70 of
the fourth embodiment. Further, in the clamping mechanism 90, the
biasing members 92 serve to elastically bias the first and second
movable platens 20, 26 in the direction away from each other, so
that it is possible to surely prevent the unstable travel of the
first movable platen 20. Accordingly, the first movable platen 20
is able to stably and smoothly move in translation or parallel
displacement during the mold opening process, without being
affected by the strain and/or tilting in the second movable platen
26, so that it is possible to maintain, highly accurately, the
parallelism between the mold attaching surfaces 14a, 20a of the
stationary platen 14 and the first movable platen 20, as well as
the parallelism between the stationary mold 16 and the movable mold
22, and thus to increase the life of the ball spline structure.
[0100] It should be noted that the biasing member 92 as described
may be adopted in the clamping mechanism 60 (FIG. 6) or the
clamping mechanism 80 (FIG. 10). In this configuration, the
unstable motion of the first movable platen 20 is also surely
resolved. Further, a receptacle hole portion for receiving the
biasing member 92 may be formed in the second movable platen
26.
[0101] FIGS. 15A to 17 show a clamping mechanism 100 according to a
seventh embodiment realizing the second concept of the present
invention. The clamping mechanism 100 of the seventh embodiment has
a configuration substantially identical to the clamping mechanism
70 of the fourth embodiment, except for the provision of a biasing
member elastically biasing the first and second movable platens in
a direction toward each other. Therefore, corresponding components
are denoted by common reference numerals and the detailed
descriptions thereof are not repeated.
[0102] The clamping mechanism 100 includes a stationary platen 14
mounted on a bed 12; a first movable platen 20 arranged movably
relative to the stationary platen 14 along the guiding axis 18a of
a guide bar 18; a support structure 24 having a ball spline
structure and movably supporting the first movable platen 20 on the
guide bar 18 along the guiding axis 18a; a second movable platen 26
separate from the first movable platen 20, and arranged movably
relative to the stationary platen 14 along the guiding axis 18a; a
connecting member 28 connecting the first movable platen 20 and the
second movable platen 26 to each other in a manner shiftable along
the guiding axis 18a relative to each other; and a biasing member
102 interposed between the first movable platen 20 and the second
movable platen 26 and elastically biasing the first and second
movable platens 20, 26 toward each other along the guiding axis 18a
(FIG. 16).
[0103] As shown in FIGS. 15A and 15B, the biasing member 102 is
formed from an elastic element such as a compression coil spring,
and elastically biases the first and second movable platen 20, 26
toward each other at the position of the connecting member 28. In
the illustrated embodiment, two biasing members 102 formed from
compression coil springs are respectively provided to the two
connecting members 28 provided at locations in proximity with the
centers of the movable platens 20, 26 (FIG. 16).
[0104] Each biasing member 102 is received in the larger-diameter
hole portion 62a of a stepped through-hole 62 in the first movable
platen 20, and is abutted at one end thereof to the shoulder face
62c of the stepped through-hole 62 and at the other end to the head
28a of the corresponding connecting member 28, so that the biasing
member 102 is arranged to surround the stem 28b of the connecting
member 28. Consequently, the biasing members 102 bias the first
movable platen 20 relative to the second movable platen 26 in the
direction toward the end frame 32 (shown by an arrow y).
[0105] In a state where the second movable platen 26 is in close
contact with the first movable platen 20 as shown in FIG. 15A
(corresponding to the mold clamping state shown in FIG. 16), the
biasing member 102 is compressed in the larger-diameter hole
portion 62a of the stepped through-hole 62, so as to bias the first
movable platen 20 in the arrowed direction y. From this state, when
the first and second movable platens 20, 26 move toward the end
frame 32, the first and second movable platens 20, 26 are shifted
into a mutually parted state by the function of the connecting
member 28 as already described (FIG. 15B). In this state
(corresponding to the mold opening state shown in FIG. 17), the
biasing member 102 is also compressed in the larger-diameter hole
portion 62a of the stepped through-hole 62 to bias the first
movable platen 20 in the arrowed direction y, and thus acts to
reduce the space between the first and second movable platens 20,
26.
[0106] Referring to FIG. 17, when the toggle unit 44 is driven to
move the second movable platen 26 and the first movable platen 20
in a mold-opening direction (shown by an arrow a), the second
movable platen 26 first starts moving toward the end frame 32 along
the tie bars 18 under the support of the sliding bearing structure.
In this connection, the first movable platen 20 is connected to the
second movable platen 26 through the "play" obtained by the
connecting members 28, but is biased toward the second movable
platen 26 under the elastic biasing force of the biasing members
102. As a result, before the second movable platen 26 moves by the
distance corresponding to the "play", the first movable platen 20
starts moving toward the end frame 32 along the tie bars 18 under
the support of the support structure 24 having the ball spline
structure, while being pulled by the connecting members 28, and
thus the molds 16, 22 are opened.
[0107] Thus, during a period from an instant when the second
movable platen 26 starts moving to an instant when the first
movable platen 20 starts moving, as well as during a period when
the first movable platen 20 moves together with the second movable
platen 26 through the connecting members 28, the biasing members
102 continue to elastically bias the first movable paten 20 toward
the second movable platen 26. Consequently, it is possible to
effectively suppress an unintentional unstable travel of the first
movable platen 20, by the elastic biasing force of the biasing
members 102, which may otherwise be caused due to the mutual
parting action of the first and second movable platens 20, 26.
[0108] It will be appreciated that the clamping mechanism 100
having the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanism 70 of
the fourth embodiment. Further, in the clamping mechanism 100, the
biasing members 102 serve to elastically bias the first and second
movable platens 20, 26 in the direction toward each other, so that
it is possible to surely resolve the unstable travel of the first
movable platen 20. Besides, the biasing members 102 further serve
to resolve minute backlash of the connecting members 28, which may
otherwise generate due to a mutual contact between the head 28a of
the connecting member 28 and the shoulder face 62c of the stepped
through-hole 62. Accordingly, the first movable platen 20 is able
to stably and smoothly move in translation or parallel displacement
during the mold opening process, without being affected by the
strain and/or tilting in the second movable platen 26, so that it
is possible to maintain, highly accurately, the parallelism between
the mold attaching surfaces 14a, 20a of the stationary platen 14
and the first movable platen 20 as well as the parallelism between
the stationary mold 16 and the movable mold 22, and thus to
increase the life of the ball spline structure.
[0109] It should be noted that the biasing member 102 as described
may be adopted in the clamping mechanism 60 (FIG. 6) or the
clamping mechanism 80 (FIG. 10). In this configuration, the
unstable motion of the first movable platen 20 is also surely
resolved.
[0110] FIGS. 18 and 19 show a clamping mechanism 110 according to
an eighth embodiment realizing the second concept of the present
invention. The clamping mechanism 110 of the eighth embodiment has
a configuration substantially identical to each of the clamping
mechanisms 90, 100 of the sixth and seventh embodiments, except for
the provision of both biasing members 100, 102 provided
respectively in the clamping mechanisms 90, 100. Therefore,
corresponding components are denoted by common reference numerals
and the detailed descriptions thereof are not repeated.
[0111] The clamping mechanism 110 includes a stationary platen 14
mounted on a bed 12; a first movable platen 20 arranged movably
relative to the stationary platen 14 along the guiding axis 18a of
a guide bar 18; a support structure 24 having a ball spline
structure and movably supporting the first movable platen 20 on the
guide bar 18 along the guiding axis 18a; a second movable platen 26
separate from the first movable platen 20, and arranged movably
relative to the stationary platen 14 along the guiding axis 18a; a
connecting member 28 connecting the first movable platen 20 and the
second movable platen 26 to each other in a manner shiftable along
the guiding axis 18a relative to each other; and biasing members
100, 102 interposed between the first movable platen 20 and the
second movable platen 26 and elastically biasing the first and
second movable platens 20, 26 away from and toward each other along
the guiding axis 18a, respectively (i.e., in opposing
directions).
[0112] Referring to FIG. 19, when the toggle unit 44 is driven to
move the second movable platen 26 and the first movable platen 20
in a mold-opening direction (shown by an arrow a), the second
movable platen 26 first starts moving toward the end frame 32 along
the tie bars 18 under the support of the sliding bearing structure.
In this connection, the first movable platen 20 is connected to the
second movable platen 26 through the "play" obtained by the
connecting members 28, but is in an elastically "floating"
condition in relation to the second movable platen 26 under the
opposing elastic biasing forces of the biasing members 92, 102. As
a result, before the second movable platen 26 moves by the distance
corresponding to the "play", the first movable platen 20 starts
moving toward the end frame 32 along the tie bars 18 under the
support of the support structure 24 having the ball spline
structure, while being pulled by the connecting members 28, and
thus the molds 16, 22 are opened.
[0113] Thus, during a period from an instant when the second
movable platen 26 starts moving to an instant when the first
movable platen 20 starts moving, as well as during a period when
the first movable platen 20 moves together with the second movable
platen 26 through the connecting members 28, the biasing members
92, 102 continue to elastically "float" the first movable paten 20
relative to the second movable platen 26. Consequently, it is
possible to effectively suppress, by the elastic biasing force of
the biasing members 92, 102, not only an unintentional unstable
travel of the first movable platen 20, which may otherwise be
caused due to the mutual parting action of the first and second
movable platens 20, 26, but also an unintentional unstable travel
of the first movable platen 20, which may otherwise be caused due
to the mutual abutting action of the first and second movable
platens 20, 26 during the translation motion.
[0114] It will be appreciated that the clamping mechanism 110
having the above configuration possesses characteristic effects
substantially identical to those of the clamping mechanisms 90, 100
as described above, and also possesses both of the advantages of
the clamping mechanisms 90, 100.
[0115] It should be noted that the elastic biasing force of the
biasing members 92, 102 is required to be adjusted into smaller
than the driving force of the drive section 30, so as not to affect
the clamping operation of the molds 16, 22. Also, the biasing
members 92, 102 may be formed from elastic elements other than the
spring, such as rubbers.
[0116] While the invention has been described with reference to
specific preferred embodiments, it will be understood by those
skilled in the art that various changes and modifications may be
made thereto without departing from the spirit and scope of the
following claims.
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